Impact wrench mechanism

ABSTRACT

A rotary impact wrench mechanism having a hammer including a hammer carrier carrying a pivoted hammer dog rotating around an anvil. The hammer carrier includes a pair of axially spaced plates interconnected by the pivot pin for the hammer dog fitting in aligned bores in the plates with a loose fit allowing the pivot pin and hammer dog to rock slightly along the axis of the pivot pin.

United States Patent Inventor Edward L. Allen Athens, Pa.

Appl. No 836.019

Filed June 24, 1969 Patented Jan. 26, 1971 Assignee Ingersoll-Rand Company New York, N.Y. a corporation of New Jersey lMPACT WRENCH MECHANISM 4 Claims, 5 Drawing Figs.

US. Cl l73/93.5 Int. Cl B25d 15/00 Field of Search 173/935, 93

i ll

References Cited UNITED STATES PATENTS 2,663,395 12/1953 Schmid 9/1955 Jimerson 8/1957 Schmid 5/1967 Vaughn Primary Examiner-James A. Leppink Atz0rneys-Carl R. Horten and David W4 Tibbott to rock slightly along the axis of the pivot pin.

pmmfinmzsmn 3557x384 INVENTOR EDWARD L. ALLEN EM MW ATTORNEY IMPACT WRENCH MECHANISM BACKGROUND OF INVENTION This invention relates to rotary impact clutch mechanisms for use in rotary impact wrenches and more particularly to rotary impact clutch mechanisms of the type having a hammer dog pivoted on a longitudinally extending pivot which is radially offset from the hammer axis and which tilts alternately between impact and nonimpact positions as the hammer rotates around the anvil located within the hammer on the hammer axis.

The US. Pat. No. 2,718,803 issued to F. A. Jimmerson discloses a rotary impact wrench mechanism containing a hammer dog pivoted in a hammer cage or carrier. The hammer carrier is composed ofa one-piece casting including a pair of axially spaced end plates rigidly interconnected by a longitudinal web. This casting is relatively expensive and is subject to breakage. It is thought that breakage often occurs as a result of the uneven loads placed on the casting by the hammer dog during impact.

SUMMARY OF INVENTION The principal object of this invention is to substantially overcome or minimize the above problems with the conventional one-piece hammer carrier using a casting.

Other important objects of this invention are: to provide a novel hammer carrier which eliminates the prior art one-piece casting and which allows the hammer dog to adjust itself to an impact with the anvil without unduly loading the carrier; and to provide a novel hammer mechanism.

The above objects are generally attained by making the hammer carrier of two separate axially spaced plates and interconnecting these plates by a means that allows the hammer dog to rock slightly on its axis so that it automatically adjusts itself during impact with the anvil jaw without placing unduly high loads on the hammer carrier. In one example, the pivot pin for the hammer dog interfrts in aligned bores in said plates and is the sole member holding the plates together for rotation in unison. The hammer pin has a relatively loose fit in the bores which allows the spaced plates to rotate relative to each other slightly, thereby allowing the hammer dog to rock slightly on its axis.

BRIEF DESCRIPTION OF DRAWING The invention is described in connection with the accompanying drawing wherein:

FIG. I is a longitudinal and vertical section of a rotary impact wrench containing the improved impact clutch mechanism;

FIG. 2 is an exploded perspective view on an enlarged scale of the impact clutch mechanism;

FIG. 3 is a section taken on line 3-3 in FIG. 1;

FIG. 4 is a section similar to FIG. 3 and showing another position of the impact clutch mechanism; and

FIG. 5 is a section similar to FIGS. 3 and 4 and showing the impact clutch mechanism at the moment ofimpact.

DESCRIPTION OF PREFERRED EMBODIMENT The rotary impact wrench l in FIG. 1 comprises a casing 2 including a pistol-grip handle 3 and a front nose 4. The handle 3 contains a fitting 5 adapted to be attached to a pneumatic pressure supply hose (not shown) and a trigger 6 actuating a valve 7 controlling the pneumatic pressure. The pneumatic pressure drives a rotary motor 8 having a drive shaft 9. The drive shaft 9 drives a spindle 10 through a rotary impact wrench clutch or mechanism 11. The spindle 10 is adapted to be connected to sockets (not shown) for driving various sizes of fasteners. All of the foregoing structure is conventional in the art of rotary impact wrenches.

The impact mechanism ll includes a central anvil formed integrally with the spindle l0 and rotating on the axis of the impact mechanism. The anvil 15 carries an anvil jaw 16 projecting radially from the anvil 15. The anvil jaw 16 has a cross section shaped like a segment of a circle and may be considered fan-shaped and comprises a pair of angularly spaced radially extending impact shoulders 17. The anvil 15 is rotatably supported on its forward portion in a bearing 18 located in the front nose 4. The rear end of the anvil I5 is rotatably supported in a driver cam 20 splined on the drive shaft 9 of the motor 8.

A hammer 21 rotates around the anvil l5 and includes a hammer carrier 22 formed by a pair of axially spaced plates 23 and 24. The rear hammer plate 23 is rotatably mounted on the driver cam 20 and the front hammer plate 24 is rotatably mounted on the anvil 15. The two hammer plates 23 and 24 are connected together by a hammer pin 25 which slidably fits in aligned bores 26 provided in the two plates 23 and 24. The pin 25 is the sole member causingthe two plates 23 and 24 to rotate in step, i.e., they are not rigidly interconnected by other means. The clearance between the pin 25 and the bores 26 can vary between .OOl inches and .005 inches; hence, it is a sliding-fit clearance which allows the pin 25 to tilt slightly in the bores 26, thereby allowing the pin to rock slightly out of exact parallelism with the axis of the anvil l5 and hammer 2].

Even ifthe pin 25 did not have the sliding lit in the plates 23 and 24, it is believed that the two plates 23 and 24 could rotate relative to each other sufficiently to allow the pin 25 to adjust itself slightly relative to the anvil axis. This is true because of the relatively flexible interconnection between the two plates 23 and 24 provided 'by the pin 25. In addition, it is believed that the plates 23 and 24 could be interconnected by more than one pin and still be able to rotate slightly relative to each other to achieve the purposes of this invention. In other words, the gist of this invention is the idea of making the hammer carrier 22 of two spaced plates 23 and 24 and interconnecting such plates together by means that allows the plates to rotate relative to each other for a slight amount.

A hammer dog 28 is rotatably mounted on the hammer pin 25 and carries a pair of impact surfaces 29 adapted to engage and impact with the anvil jaw 16 periodically as it rotates around the anvil 15. The hammer dog 28 carries a cam projection 30 extending from its rear end adapted to engage the driver cam 20. The driver cam 20 cooperates with the cam projection 30 to urge the hammer dog 28 to a disengaged position with the anvil 15 immediately before each impact.

FIGS. 3 to 5 illustrate the operation of the engagement of the hammer dog 28 with the anvil l5. Immediately after impact, the torque on the driver cam 20 swings the hammer dog 28 to a disengaging position. For those unfamiliar with the operation of this type of mechanism, it is explained in US. Pat. No. 2,718,803 issued to F. A. Jimmerson.

By making the hammer carrier 22 of two spaced plates 23 and 24 connected nonrigidly together by the hammer pin 25, with the hammer pin 25 having a sliding fit" in the plates, these plates 23 and 24 can rotate relative to each other slightly allowing the hammer pin 25 to rock slightly relatively to a position in exact parallelism with the axis of the anvil. It is believed that this slight rocking movement of the hammer pin 25 allows the hammer dog 28 to rock lengthwise relative to the anvil axis so that the hammer surfaces 29 can automatically mate with the anvil jaw shoulders 17 without placing unduly high stresses on the hammer plates 23 and 24. Hence, it is believed that the ability of the plates 23 and 24 to rotate relative to each other slightly, rather than being rigidly fixed together, is an improvement in a rotary impact wrench mechanism.

Another advantage provided by making the carrier 22 of two spaced plates 23 and 24 locked together nonrigidly by the pin 25 is that it allows the hammer dog 28 to swing freely without interference from an interconnecting web on the carrier 22, as is the problem in the prior art. Thus, the hammer dog 28 can be arranged in various shapes and sizes which could not be done with the conventional carrier. This freedom to shape the hammer dog 28 enables a designer to provide the hammer mechanism with better balance characteristics.

Although a single embodiment of the invention is illustrated and described in detail, it will be understood that the invention contemplates other embodiments and variations covered by the attached claims.

lclaim:

1. An impact clutch mechanism for a rotary impact mechanism comprising:

an anvil having an impact jaw rotatable about an anvil axis and adapted to drive a fastener;

a hammer rotatable on said anvil axis about said anvil jaw and including a pair of axially spaced plates pivoted on said anvil axis, a pivot axis extending between said plates and being offset from said anvil axis and a hammer dog pivoted on pivot means interconnected to said plates for swinging about said pivot axis between alternate positions of impacting and nonimpacting with said anvil jaw; and

interconnection means nonrigidly holding said plates together for rotation in unison and including said pivot means, said plates and said interconnection means cooperating to allow the pivot axis of said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.

2. An impact clutch mechanism for a rotary impact mechanism comprising:

an anvil having an impact jaw rotatable about an anvil axis and adapted to drive a fastener;

a hammer rotatable on said anvil axis about said anvil jaw and including a pair of axially spaced plates pivoted on said anvil axis, a pivot axis extending between said plates and being offset from said axis and a hammer dog pivoted on pivot means interconnected to said plates for swinging about said pivot axis between alternate positions of impacting and nonimpacting with'said anviljaw; and

said hammer dog and its pivot means being the sole interconnection holding said plates together for rotation in unison, said plates and said interconnection cooperating to allow the pivot axis of said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.

3. An impact clutch mechanism for a rotary impact mechanism comprising;

an anvil having an'impact jaw rotatable about an anvil axis and adapted to drive a fastener;

a hammer rotatable on said anvil axis about said anvil jaw said pivot pin being connected to said plates and being the sole memberholding said plates together for rotation in unison, said plates and said pivot pin cooperating to allow the pivot axisof said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.

4. The impact clutch mechanism of claim 3 wherein said pivot pin is connected to said plates by slidably interfitting in longitudinally aligned bores in said plates and having a relatively loose fit in said bores thereby allowing said pin to tilt slightly in said bores. 

1. An impact clutch mechanism for a rotary impact mechanism comprising: an anvil having an impact jaw rotatable about an anvil axis and adapted to drive a fastener; a hammer rotatable on said anvil axis about said anvil jaw and including a pair of axially spaced plates pivoted on said anvil axis, a pivot axis extending between said plates and being offset from said anvil axis and a hammer dog pivoted on pivot means interconnected to said plates for swinging about said pivot axis between alternate positions of impacting and nonimpacting with said anvil jaw; and interconnection means nonrigidly holding said plates together for rotation in unison and including said pivot means, said plates and said interconnection means cooperating to allow the pivot axis of said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.
 2. An impact clutch mechanism for a rotary impact mechanism comprising: an anvil having an impact jaw rotatable about an anvil axis and adapted to drive a fastener; a hammer rotatable on said anvil axis about said anvil jaw and including a pair of axially spaced plates pivoted on said anvil axis, a pivot axis extending between said plates and being offset from said axis and a hammer dog pivoted on pivot means interconnected to said plates for swinging about said pivot axis between alternate positions of impacting and nonimpacting with said anvil jaw; and said hammer dog and its pivot means being the sole interconnection holding said plates together for rotation in unison, said plates and said interconnection cooperating to allow the pivot axis of said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.
 3. An impact clutch mechanism for a rotary impact mechanism comprising; an anvil having an impact jaw rotatable about an anvil axis and adapted to drive a fastener; a hammer rotatable on said anvil axis about said anvil jaw and including a pair of axially spaced plates pivoted on said anvil axis, a pivot pin extending between said plates and being offset from said anvil axis and a hammer dog mounted on said pivot pin and swingable between alternate positions of impacting and nonimpacting with said anvil jaw; and said pivot pin being connected to said plates and being the sole member holding said plates together for rotation in unison, said plates and said pivot pin cooperating to allow the pivot axis of said hammer dog to rock slightly relative to the anvil axis allowing said hammer dog to automatically adjust itself during impact with said anvil jaw without placing dangerous loads on said hammer.
 4. The impact cLutch mechanism of claim 3 wherein said pivot pin is connected to said plates by slidably interfitting in longitudinally aligned bores in said plates and having a relatively loose fit in said bores thereby allowing said pin to tilt slightly in said bores. 